Electromagnetic wave energy absorbing elements for use in high frequency electron discharge devices having traveling wave tube sections



NOV. 19, 1968 RALLEN ET AL R 3,412,279

ELECTROMAGNETIC WAVE ENERGY ABSGRBING ELEMENTS FOR USE IN HIGH FREQUENCYELECTRON DISCHARGE DEVICES HAVING TRAVELING WAVE TUBE sEcTIoNs 2Sheets-Sheet 1 Filed Sept. 13, 1965 INVENTO RS RICHARD R. ALLEN RODNEY RBUBERT BY Ail /TORNEY United States Patent 3,412,279 ELECTROMAGNETICWAVE ENERGY ABSORBIN G ELEMENTS FOR USE IN HIGH FREQUENCY ELECTRONDISCHARGE DEVICES HAVING TRAVELING WAVE TUBE SECTIONS Richard R. Allen,Redwood City, and Rodney R. Rubert, Santa Clara, Calif., assignors toVarian Associates, Palo Alto, Calif., a corporation of California FiledSept. 13, 1965, Ser. No. 486,924 9 Claims. (Cl. 315-35) ABSTRACT OF THEDISCLOSURE Electromagnetic wave energy absorbing elements (attenuators)for use in high frequency electron discharge devices, particularlytraveling wave type devices, and a specific means for mounting andcooling such elements are disclosed. Various structural embodiments ofsuch electromagnetic wave energy absorbing elements are described asincorporated into certain specific types of high frequency electrondischarge devices.

This invention relates in general to improvements in high frequencyelectron discharge devices incorporating traveling wave interactionsections and more particularly to novel means for fluid cooling lossyelectromagnetic wave energy absorbing elements utilized in highfrequency electron discharge devices which fluid cooling means servesthe additional function of providing suflicient fluid pressure on thedefining walls for said lossy elements such as to obviate the necessityof utilizing conventional brazing techniques to retain said lossyelements in situ.

High frequency electron discharge devices incorporating traveling waveinteraction sections conventionally employ circuit sever portions alongthe active circuit length thereof in order to prevent undesiredoscillations in operation. These circuit severs can take many forms oneof which is the utilization of lossy attenuator materials for absorbingelectromagnetic Wave energy at the severed region. In Ia conventionalforward wave amplifier traveling wave tube such circuit severs areutilized both for absorbing fonward wave traveling wave energy in theinput or upstream portions of the traveling wave tube and for absorbingbackward traveling wave energy in the down stream or output portions ofthe tube. In a hybrid type of electron discharge device wherein aklystron input section is utilized in conjunction with a traveling Waveoutput section the utilization of a circuit sever between the klystronand traveling wave sections is primarily for the absorption of backwardwave energy in a forward wave amplifier. Further circuit severs in thetraveling wave tube section may also be utilized in a conventionalmanner.

Common problems encountered with circuit severs of the prior art typeutilizing lossy ceramic attenuator discs for absorbing electromagneticwave energy at the severed regions are destruction of the lossy discsdue to arcing problems encountered in use, fabrication difficultiesencountered during the brazing operations to maintain a rigidpositioning of the ceramic discs Within a particular portion of thetraveling wave circuit sever portion and power handling limitationsinherent with the utilization 3,412,279 Patented Nov. 19, 1968 of aceramic lossy material. These and other problems of the prior art areobviated by the teachings of the present invention which providesutilization of fluid pressure to maintain a rigid mechanical jointbetween the lossy ceramic absorbing discs and their respective definingwalls. The present invention furthermore eliminates the utilization ofany metallurgical brazes and so forth which require extensive and timeconsuming brazing cycles in the fabrication of the slow wave circuitsever portions by the utilization of the aforementioned fluid pressuremlaintenance technique. The present invention furthermore provides greatincreases in power handling capabilities for the prior art types oflossy ceramic discs by the use of the aforementioned fluid cooling andpressure techniques.

It is therefore an object of the present invention to provide animproved high frequency electron discharge device incorporating novelfluid cooled electromagnetic wave energy absorption means.

A feature of the present invention is the provision of a high frequencyelectron discharge device including an electron beam-wave interactionsection having incorporated therein a lossy electromagnetic wave energyabsorption element provided with novel fluid cooling means therefor.

Another feature of the present invention is the provision of a highfrequency electron discharge device incorporating an electromagneticwave energy interaction section including lossy electromagnetic waveenergy attenuating means having novel cooling provisions therefor, saidcooling provisions serving to rigidly maintain said lossy means withinsaid interaction circuit portion by means of fluid pressure.

Another feature of the present invention is the provision of a highfrequency electron discharge device incorporating a traveling waveinteraction section having a circuit sever portion which includes atleast a plurality of lossy electromagnetic wave energy absorptionelements, said lossy electromagnetic wave energy absorption elementsbeing provided with fluid cooling channels along the major transversedimensions thereof in a rnann er such that said fluid cooling channelsserve to fixedly maintain said lossy attenuating elements in place bymeans of the effective hydrostatic pressure of collant fluid flowingwithin said coolant channels.

Another feature of the present invention is the provi sion of a highfrequency electron discharge device incorporating Ia traveling waveinteraction section having a lossy electromagnetic wave energyabsorption element disposed therein, said lossy absorption element beingprovided with fluid coolant means along a major dimension thereof, saidfluid coolant means comprising a fluid flow channel separated from saidmajor dimension of said lossy wave energy absorbing element via theinterrnediary of a deformable wall portion.

These and other features and advantages of the present invention willbecome more apparent upon a persual of the following specification takenin conjunction with the accompanying drawings wherein:

FIG. 1 is a fragmentary longitudinal view of a traveling wave tubepartly in elevation, partly in cross-section which incorporates thenovel fluid cooled lossy attenuator wave energy absorption means of thepresent invention,

FIG. 2 is a cross-sectional view partly in elevation 3 taken along thelines 22 of the traveling wave tube depicted in FIG. 1,

FIG. 3 is a cross-sectional view partly in elevation taken along theline 33 of the section depicted in FIG. 2,

FIG. 4 depicts a fragmentary cross-sectional view partly in elevation ofan alternative fluid cooled circuit sever section incorporating thetechniques of the present invention,

FIG. 5 is a fragmentary longitudinal elevational view of a hybridmicrowave amplifier incorporating the teachings of the presentinvention,

FIG. 6 is a cross-sectional view partly in elevation taken along theline 66 of FIG. 5,

FIG. 7 is a cross'sectional view partly in elevation taken along theline 77 of the section of FIG. 6,

FIG. 8 is an alternative wave energy absorption portion utilized betweenthe klystron and traveling wave tube sections in a hybrid amplifierincorporating the teachings of the present invention, and

FIG. 9 is a cross-sectional view taken along the line 99 of FIG. 8 inthe direction of the arrows.

Referring now to FIG. 1 there is depicted a high frequency electrondischarge device 11 of the traveling wave type incorporating a beamforming and projecting means 12 disposed at the upstream portion thereofand an electron beam collector 13 disposed at the downstream portionthereof. Intermediate the upstream and downstream portions of thetraveling wave tube 11, slow wave circuit sections 14 and 15 of theclover-leaf type, more fully disclosed in an article by M. Chodorow etal. entitled, Some New Circuits for High Power Traveling Wave Tubes,Proc. I.R.E., August 1957, pps. 1106-1118, are located. One or morecircuit sever sections such as 16, 17 may be incorporated between theupstream and downstream portions of the traveling wave tube of FIG. 1for absorbing electromagnetic wave energy for purposes of stabilizationin a manner well known in the art. The electron beam forming andprojecting means 12 preferably is a conventional Pierce-type gun whichincludes a focusing anode 18, a main accelerating anode 19 and anelectron emission surface or cathode, not shown. Since the detailsthereof are well known, no further discussion of the same will be madeherein.

Turning now to the particular details of the circuit sever portions 16and 17, reference to FIGS. 2 and 3 will now be made for enumerationthereof. In a traveling wave tube of the type depicted in FIGS. 1-3, itis common practice to utilize a plurality of lossy attenuator elementssuch as 20, 21, 22, 23 in both the upstream sever section 16 and thedownstream sever section 17. The specific purpose of the lossyattenuator elements in the upstream sever section 16 are to absorb allelectromagnetic wave energy present in the input slow wave circuitportion 14 and to allow only the current density modulated electron beamto pass therethrough to the downstream portions of the tube forstabilization purposes in a manner well known in the art. The particularpurposes of the lossy ceramic elements in the downstream circuit severportion 17 in a forward wave amplifier tube such as depicted in FIG. 1is to completely absorb any backward traveling wave energy produced inthe downstream section 15 in order to stabilize the tube in a mannerwell known in the art. Many problems have heretofore been encounteredwith the utilization of lossy ceramic discs used for the attenuatormeans which heretofore have been conventionally made of ceramic loadedcarbon with regard to the metallurgical techniques utilized to secure arigid bond between the lossy elements and the transverse defining walls24, 25 of clover-leaf cavity 30. A typical brazing operationtherebetween may take four to five hours and result in costs of perhaps$100 per tube per brazing cycle. Inherent in the utilization ofmetallurgical brazing between the transverse defining walls 24, 25 andthe major faces of each lossy ceramic element are the differentialexpansion problems occurring therebetween in use which very often resultin cracking of the lossy ceramic element itself under high poweroperating conditions and/or during the brazing cycle itself.Furthermore, imperfections in the bond may occur which would result inseparations occur ring between one or the other or both of the definingwalls 24, 25 and the respective major faces of the ceramic elementswhich renders the disc susceptible to breakdown due to high power arcingin use. Further problems encountered in the utilization of lossy ceramicelements such as 20, 22, etc., have been the power handling limitationsinherent in such discs. Power handling capabilities are improved bybetter than a factor of two by the utilization of fluid coolant flowchannels 28 separated from one or the other of the major faces of thelossy discs via the intermediary of a thermally conductive deformablewall portion 29.

In a traveling wave tube such as the type depicted in FIG. 1 whichutilizes a clover-leaf slow wave circuit and includes a plurality ofsubstantially circular periodic sections or cavities 30, of clover-leafconfigurations, each cavity 30 is defined by a pair of spaced transverseend wall portions such as 24, 25, 26, etc. Each end wall has an annularbeam passage aperture 32 axially disposed therein which also serves as acapacitive coupling between sections. Each clover-leaf section or cavity30 includes a sinuous four element clover-leaf side wall, such as 33,which is generally brazed between the aforementioned transverse endwalls of each clover-leaf section 30 and which includes four spacerotated radially oriented and inwardly directed finger portions 33'.Each of the transverse end walls 24, 26, etc., with the exception of theone sever end wall 25, includes a plurality of coupling apertures suchas 34 to provide a negative mutual inductive coupling between sectionsin order to provide a forward wave amplifier having high interactionimpedance characteristics in a manner well known in the art. See forexample, US. patent application Ser. No. 7,481 entitled, ConductiveCoupling Means and Methods for High Frequency Apparatus, filed Feb. 8,1960, by M. Chodorow, now US. Patent 3,233,139, assigned to the sameassignee as the present invention.

The circuit sever section 16 is formed by loading the last clover-leafsection or cavity 30 with four 90 space rotated lossy attenuatorelements 20, 21, 22, 23 disposed in cut-out portions at the ends of eachof fingers 33, and brazing said elements along their major facedimensions to the transverse defining walls 24, 25 by means of anysuitable brazing materials such as molybdenum-manganese. Such prior artlossy elements have been found to be capable of handling around 10kilowatts average power before destruction thereof set in due to arcingif loosened or simple excessive heating due to inadequate prior artfluid cooling mechanisms connected therewith. By providing a fluidcoolant channel such as 28, having a cross-sectional configurationconforming to the major dimension or major face, e.g., 22, of the lossydiscs 20-23, excellent cooling thereof is achieved in use and CW powersup to 20 kilowatts and above are easily handled according to theteachings of the present invention. Furthermore, multimegawatt pulsepowers are easily handled when fluid coolant flow channels are disposedadjacent the major face of the lossy elements in thermal conductive heattransfer relationship as shown in FIGS. 2 and 3.

A typical example of a suitable lossy attenuator material used for discs20-23 is carbon loaded alumina ceramic. Other lossy materials which havebetter thermal conductivities than carbon loaded alumina ceramic areloaded porous beryllium oxide ceramics and loaded forsterite ceramicswhich, however, require in the case of the beryllium oxide ceramics,special enclosed furnaces to handle the toxic vapors generated in thebrazing operation and which in the case of the forsterite ceramicspresent breakage and cracking problems at the brazed joint due to poorthermal shock resistance and poor impact strength, By utilizing thefluid coolant flow channels and eliminating the brazing operations manyof the problems heretofore encountered are obviated and the tubedesigner is given greater design choices which are not burdened bymetal-to-ceramic bonding considerations. Ordinary tap water emanatingfrom a city water supply system will provide 80 p.s.i. pressurecapabilities and thus the T-junction input coupling port 37 may be tiedinto any typical city water supply system preferably via a commonmanifold system which is generally utilized to couple all fluid cooledportions of the device together. Any suitable water pump capable ofmaintaining a 40 p.s.i. effective hydrostatic pressure on the deformablewalls may obviously be used to supply the coolant fluid. The terminologyeffective hydrostatic pressure is utilized herein to define the fluidpressure in p.s.i. exerted on the deformable wall portion by thepressure of the coolant fluid flowing through the coolant flow channels.For example, if a standpipe were substituted for a deformable wallportion such as 29 and oriented vertically, a 40 p.s.i. fluid pressurecaused by coolant fluid flowing through coolant flow channel 28 wouldproduce a 90foot head in the standpipe. Hence the terminology effectivehydrostatic pressure is appropriate to define the pressure exerted byflowing fluid. Obviously the example of 40 p.s.i. is not to be taken ina restrictive sense since innumerable variations in the paramtersinvolved which will produce effective compressive forces on the capturedlossy elements would be readily apparent to one skilled in the art.Therefore the following example is merely illustrative of a specificembodiment.

The breakage problems heretofore encountered and the problems due tocracking of the discs and separation thereof from the transversedefining walls 24, are still present if conventional brazing methods areutilized to maintain the lossy attenuator elements in place as statedabove. Therefore, according to the teachings of the present inventionthe common defining wall of flow channel 28 separating the major facesof the lossy elements 20 from the channel, e.g., 28, is made to conformto the dimensions of the element 20 and to have a thickness which issufliciently thin to permit the wall to be deformed by fluid pressure ofthe fluid coolant flowing through flow channels 28 to thereby obtain avery rigid sandwich construction through compression of said elementswhich will not loosen in use and which does not require any brazingoperations. Effective hydrostatic pressures of approximately 40 p.s.i.(pounds per square inch) when utilizing copper for the deformable wallportion 29 of approximately .025 inch thick in conjunction with one-inchdiameter discs have been found quite satisfactory to achieve theaforementioned rigid sandwiched construction.

The coolant flow channels 28 can be interconnected in various ways asshown more clearly hereinafter. For example, in FIG. 2 two copper or thelike tubulations 36 are used to interconnect adjacent flow channels 28to permit a unidirectional fluid flow therethrough. Coolant fluid suchas tap water is coupled via a T-junction 37 along copper or the liketubes 38, 39 into channels 28 via fluid coupling ducts 40 in theembodiments of FIGS. 2 and 3 which are located in the enlarged flangedextions 41 of the transverse defining wall 25. Coolant flow channels 28are enlarged to conform to the major dimensions of each of the lossyelements as best seen in FIG. 2 and fluid coupling members such as tubes35, 36 of reduced dimensions are utilized to couple the fluid into theremaining two channels 28 whence a similar output coupling arrangementemploying a T-junction 42 in conjunction with tubes 43, 44 is utilizedto remove the coolant fluid from the sever section. In the embodiment ofFIGS. 2 and 3 the downstream end wall of each of the channels 28 isformed by disc-shaped copper plates 45 having a handle portion 46 asshown which are brazed or the like in suitable off-set ridge portions 47in transverse wall 25, as shown. Fabrication of the cooling chan- 6 nel28 in the embodiment of FIG. 1 is thereby facilitated by simplymachining out the area conforming to the particular physicalconfiguration of the lossy elements 20-23. Circuit sever 17 can be madeidentical to section 16 and independent thereof as shown in FIGS. 1-3.

Alternatively, the circuit sever depicted in FIG. 4 may replace sections16 and 17 and has the advantage of utilizing a composite single flowchannel arrangement rather than two separate ones such as shown in theembodiment of FIGS. 1-3. Briefly, the composite circuit sever depictedin FIG. 4 includes a plurality of lossy attenuating elements 50 disposedin space rotated relationship preferably with azimuthal periodicity withrespect to the beam axis as shown in FIG. 2 in the aforementionedupstream and downstream clover-leaf end sections or cavities 51, 52,respectively, and retained therein between the transverse defining walls54, 55, 56, 57, respectively. A fluid coolant flow channel 60 is commonto both portions of the composite circuit sever depicted in FIG. 4 andobviates the necessity for the dual feed arrangements of 16 and 17 inthe embodiment of FIG. 1. The fluid coolant flow channels 60 areenlarged dimensionally relative to the fluid coupling channels denotedby 61, 62 in a manner similar to that depicted in FIG. 2 by machiningout an area of the defining walls 55, 56 conforming to the lossyelements 30 to thereby provide deformable wall portions 56'. Suitableinput and output coupling ports 63 and 64 provide ingress and egress offluid from any conventional pumping system. Once again the copperdefining walls or the like 55, 56 are dimensionally thin in the areaconforming to the major transverse dimension of the lossy attenuatorelements 50 as mentioned above in order to provide flexible ordeformable wall portions 55', 56' such that the effective hydrostaticpressure within coolant flow channels will provide the requiredoppositely directed compressive forces on the lossy elements 50 in orderto maintain a rigid sandwich construction between elements 54, 50, 55and 56, 50, 57.

The tube main body 6 and the transverse defining walls for theclover-leaf sections are advantageously made of copper or the likematerial and any suitable brazing material or other metal joiningtechniques may be employed to provide rigid vacuum tight bonds betweenthe various elements. In the embodiments of FIGS. 2 and 3 and 4, thetransverse defining walls which are subjected to a relatively highamount of pressure due to the pressure developed in the cooling channelportions 28 and 60, namely transverse walls 24 and 54 and 57 are made ofa higher strength material than copper, such as stainless steel, so asto provide a more rigid non-deformable wall portion in order to minimizeany possible variation of cavity dimensions for the cloverleaf sectionsdue to the effective hydrostatic compressive forces.

Turning now to FIG. 5 there is depicted therein a hybrid tube apparatus70 comprising a stagger tuned klystron driver section 71 followed by atraveling wave tube section 72. Since the literature is replete withdetails of stagger tuned klystrons such as section 71 and slow wavecircuits such as 72 the particular details thereof will not be specifiedfurther herein. Suffice it to say that the hybrid tube depicted in FIG.5 includes an electron beam forming and projecting means 74 disposed atthe upstream end portion thereof and a suitable electron beam collector75 disposed at the downstream end portion thereof in a manner well knownin the art. Once again, the electron beam forming and projecting means74 may comprise any suitable Pierce-type gun arrangement which includesa focusing anode 76 and an accelerating anode 77 as *well as a cathodestructure disposed within focusing anode 76 in a manner well known inthe art.

Turning now to FIGS. 6 land 7 which represent sectional views of asuitable electromagnetic wave energy absorbing section disposed betweenthe klystron section and the traveling Wave tube section of the hybridtube in FIG. 6. In order to eliminate any possible instability problemsarising in a hybrid amplifier such as depicted in FIG. 5, the travelingWave tube section 72 is terminated at its upstream end portion by meansof both a drift tube 79 coupling arrangement between the last cavity 80of the klystron section and in the case of a clover-leaf type of slowwave structure the last clover-leaf section or cavity 81. A plurality ofspatially displaced lossy attenuator elements such as carbon loadedalumina ceramic or silicon carbide, etc., are utilized to absorb allbackward traveling wave energy along the traveling wave circuit sectionin a manner well known in the art. An axial feed arrangement is utilizedin the embodiment of FIGS. 6 and 7 to inject suitable coolant fluidssuch as tap water, etc., into enlarged coolant flow channels 81, 82which generally conform to the major face dimensions of the lossyelements. Once again a pair of spaced transverse end wall members 83, 84are utilized to define the last clover-leaf section 81 and the lossyattenuator discs 85 are disposed therebetween as shown. Wall 84 ispreferably made of stainless steel as mentioned previously to withstanddeformation due to the effective hydrostatic pressures induced bycoolant fluid flowing through channel 82 and transverse wall member 83is preferably made out of copper and has a reduced thickness dimensionin the areas conforming to the lossy element major dimensions asmentioned previously such that a deformable wall portion is formed inorder to allow the compressive forces of the coolant fluid to applyfluid pressure to the wall member and thereby obtain a rigid sandwichedconstruction for the lossy elements.

An input axially directed fluid coupling port 86 is utilized to providethe coolant fluid to flow channels 82 and a plurality of reduceddimension fluid coupling channels 88, 89, 90, etc., are used tointerconnect the various enlarged fluid channel portions 82. An outputfluid cou pling port 87 is utilized in the embodiment of FIGS. 6 and 7to extract the coolant fluid from the wave energy absorption section. Asin the embodiments depicted in FIGS. 14, a effective hydrostaticpressure of approximately 40 pounds per square inch when utilized with aone-inch diameter lossy disc in conjunctionwith an approximately .025inch thick deformable copper Wall portion which defines one transverseportion of each fluid flow channel 82 has been found adequate to providean effective sandwich fit between the transverse end walls 83, 84 andthe various lossy attenuator elements. The directive arrows depicted inFIGS. 6 and 7 are utilized to illustrate the fluid flow directionsbetween input port 86 and output port 87. In lieu of the separatechannel defining members 45 uitilized for each of the enlarged channelportions 28 of the embodiments of FIGS. 2 and 3, the embodiment of FIGS.6 and 7 utilizes a transverse ring member 91 to define the upstream endwall portion of the flow channels 82 and coupling channels 88, 89, 90,etc.

In the embodiment of FIGS. 8 and 9 an alternative fluid coolingarrangement in a hybrid tube with regard to the fluid couplingarrangement is depicted. In the embodiment of FIGS. 6 and 7 abidirectional split flow arrangement is utilized Whereas in theembodiment of FIGS. 8 and 9 a unidirectional fluid flow arrangementwhich may have advantages in certain system applications is employed. Anarcuate shaped flow channel 94, best seen in FIG. 9 is utilized in theembodiment of FIGS. 8 and 9 to provide the necessary effectivehydrostatic pressure and cooling for the lossy attenuator elements 95.Input channel 92 and output channel 93 serve as coupling ports for thecoolant fluid and are connected to any suitable pumping system. Quiteobviously, the various parameters of the fluid coupling arrangementsdepicted in the embodiments of FIGS. 1, 4, 6 may be interchangeablyutilized to take advantage of the permutations and combinations thereof.Again, the lossy attenuator elements, discs 95,

are sandwiched between a pair of transverse defining end walls 97, 98with wall 97 again having reduced thickness in the area 99 common to themajor face dimensions of each of the discs. The flow channels 100 arethen coupled in a series feed arrangement via coupling flow channel 94which is segmented by radial wall portion 161 as seen in FIG. 9. Thistype of fluid feed arrangement permits the tube designer to haveincreased freedom of design such that electron discharge devicesemploying the teachings of the present invention are more easilyincorporated int-o systems having diverse spatial and coolant flowparameter requirements.

Since many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A high frequency electron discharge device including an electron beamforming and projecting means disposed at the upstream end portionthereof, electron beam collector means disposed at the downstream endportion thereof, slow wave circuit means disposed intermediate saidelectron beam forming and projecting means and said electron beamcollector means, said slow wave circuit means being adapted and arrangedto provide a cumulative energy exchange between an electron beam andelectromagnetic wave energy propagating along said slow wave circuitwithin a predetermined frequency range, said slow wave circuit meansincluding lossy attenuator means disposed therealong for absorbingelectromagnetic wave energy traveling along said slow wave circuit, saidlossy attenuator means being disposed between at least a pair of spacedtransverse conductive wall members in a sandwiched arrangement, at leastone of said transverse Wall means forming a confining surface for afluid coolant flow channel, said transverse wall means forming saidcommon boundary between said lossy attenuator means and said fluidcoolant flow channel having a thickness dimension such as to bedeformable in the presence of coolant fluid flowing through said coolantchannel whereby said lossy attenuator means is compressed between saidpair of transverse wall members by fluid pressure.

2. A high frequency electron discharge device having an electron beamforming and projecting means disposed at the upstream end portion ofsaid device and an electron beam collector means disposed at thedownstream end portion thereof, high frequency electromagnetic slow wavecircuit interaction means disposed therebct ween, said interaction meansincluding at least one lossy attenuator element for absorbingelectromagnetic Wave energy and a rigid structural member in contactwith one side of said lossy attenuator element, a fluid coolant flowchannel in contact with the other side of said lossy attenuator element,said fluid coolant flow channel having a Wall thickness dimension suchas to be deformable in the presence of coolant fluid flowingtherethrough, whereby said lossy attenuator element is maintained undercompression against said rigid structural member by means of fluidpressure in said fluid coolant flow channel.

3. A high frequency eltctron discharge device including an electron beamforming and projecting means disposed at the upstream end portionthereof and an electron collector means disposed at the downstream endportion thereof, a slow wave interaction circuit disposed between saidelectron beam forming and projecting means and said electron collectormeans along the electron beam axis of said device, said slow wavecircuit means including a circuit sever portion for absorbingelectromagnetic wave energy and permitting passage therethrough of anelectron beam, said circuit sever means including a lossy attenuatorelement fixedly secured between a pair of spaced transverse wall membersforming a portion of said slow wave interaction circuit, a fluid coolantflow channel disposed in heat transfer relationship with respect to saidlossy attenuator element, at least a portion of one of said transversewall members forming a common radial boundary with respect to the beamaxis between said lossy attenuator element and said fluid coolantchannel, said portion of said transverse wall member having a thicknesssuch as to be deformable under fluid pressure.

4. A high frequency electron discharge device including an electron beamforming and projecting means disposed at the upstream end portionthereof and an electron beam collector means disposed at the downstreamend portion thereof, an electromagnetic Wave-beam interaction meansdisposed between said beam forming and projecting means and said beamcollector means, said interaction means including lossy attenuator meansdisposed therein for absorbing electromagnetic wave energy, said lossyattenuator means including at least a pair of axially displaced lossyelements, said axially displaced lossy elements having a fluid coolantchannel disposed therebetween, the walls of said fluid coolant flowchannel having a thickness dimension such as to be deformable in thepresence of coolant fluid flow therethrough, said lossy elements beingsubjected in use to compressive forces within said interaction means byfluid pressure elfectuating deformation of said walls of said fluidcoolant flow channel.

5. A high frequency electron discharge device including an electron beamforming and projecting means disposed at the upstream end portionthereof and an electron beam collector means disposed at the downstreamend portion thereof, a slow wave interaction circuit disposed along saidelectron beam axis between said beam forming and projecting means andsaid beam collector means, said slow wave interaction circuit meansbeing provided with lossy attenuator means for absorbing electromagneticwave energy traveling on said slow wave interaction circuit means, saidlossy attenuator means including a lossy element having a major facedimension radially disposed with respect to said beam axis, said lossyattenuator element being maintained in a fixed position within said slowwave interaction circuit by being nested between a pair of transverselydisposed conductive wall members, at least one of said conductive wallmembers forming a common radial boundary between a fluid coolant flowchannel and said lossy attenuator element, said common wall portionhaving a thickness such as to be deformable by fluid pressure introducedwithin said coolant channel in use whereby said lossy attenuator elementis subjected to compressive forces due to said fluid pressure.

6. A high frequency electron discharge device having electron beamforming and projecting means disposed at the upstream end portionthereof, an electron beam collector means disposed at the downstream endportion thereof, slow wave circuit means disposed along and about saidelectron beam path for propagating electromagnetic wave energy within apredetermined frequency range in order to provide a cumulative energyexchange between the electron beam and electromagnetic wave energypropagating along said slow wave circuit means, said slow wave circuitmeans including a plurality of lossy attenuator elements disposed in atleast one portion of said slow wave circuit means, said plurality oflossy attenuator means comprising a plurality of azimuthly displaceddisc-shaped elements each of which is sandwiched between a pair ofaxially spaced conductive wall members forming a portion of said slowwave circuit means, said slow wave circuit being provided with fluidcoolant flow channels, at least one of said wall members forming acommon wall between a radial oriented major face of said disc-shapedelements and said fluid coolant flow channels, said common wall having athickness such as to be deformable by fluid pressure introduced withinsaid coolant channel in use whereby said disc shaped elements arecompressed between said pair of axially spaced conductive wall membersby fluid pressure, said fluid coolant flow channels being provided withfluid coupling channels interconnected between at least two of saidfluid coolant flow channels for at least two of said lossy attenuatorelements, means for introducing and extracting coolant fluid within saidfluid coolant flow channels and said fluid coupling channels in aunidirectional manner such that coolant fluid flows therethrough in aunidirectional manner.

7. A high frequency electron discharge device including an electrom beamforming and projecting means disposed at the upstream end portionthereof and an electron beam collector means disposed at a downstreamend portion thereof, slow wave interaction circuit means disposedintermediate said beam forming and projecting means and said beamcollector means, said slow wave interaction circuit means including atleast one cavity member formed by a pair of axially spaced transverseend walls, said cavity having side walls formed in a manner such as toprovide a clover-leaf shaped side wall configuration, said clover-leafshaped side wall configuration having at least four finger elementsradialy directed therein such as to form said clover-leaf configuration,each of said finger elements having a lossy attenuator disc disposed atthe end portions thereof and nested between said pair of transverseconducting wall members forming said cavity end walls, at least one ofsaid transverse end walls forming a common boundary between a fluidcoolant flow channel and said lossy attenuator discs, said fluid coolantflow channel having radial dimensions in the vicinity of each of saidlossy attenuator discs which encompass at least a major portion of thetransverse cross-sectional face dimension of each of said lossyattenuator dics and which have a wall thickness such as to be deformablein the presence of coolant fluid flowing therethrough, whereby saidlossy attenuator discs are maintained in compression and improved fluidcooling of said lossy attenuator discs is achieved in use.

'8. A high frequency electron discharge device including an electronbeam forming and projecting means disposed at the upstream end portionthereof and an electron beam collector means disposed at the downstreamend portion thereof, slow wave interaction circuit means disposed alongthe electron beam axis intermediate said beam forming and projectingmeans and said beam collecti-ng means, said slow wave circuit includingat least one clover-leaf shaped cavity, said clover-leaf shaped cavityhaving a pair of axially displaced transversely dis posed end wallmembers, the side walls of said cloverleaf cavity including a pluralityoffingers protruding radially therein, said fingers having lossyattenuator elements disposed at the end portions thereof, said lossyattenuator elements having fluid cooling means which include a fluidcoolant flow channel having a thickness dimension such as to bedeformable in the presence of coolant fluid flowing through said coolantchannel whereby said lossy attenuator elements are compressed betweensaid pair of end wall members.

9. A high frequency electron discharge device including an electron beamforming and projecting means disposed at the upstream end portionthereof for introducing an electron beam along a central beam axis ofsaid device, an electron beam collector means disposed at the downstreamend portion of said device, a slow wave interaction circuit meansdisposed along and about said electron beam axis between said downstreamand upstream end portions thereof, said slow wave interaction circuitmeans including at least a pair of axially spaced cavities each of whichincludes lossy attenuator elements disposed therein, said lossyattenuator elements being disposed in nesting relationship between therespective transverse end walls of each of said cavities, a fluidcoolant flow channel disposed intermediate said pair of axially 1 1 i 2spaced cavity members and dimensioned such as to prospaced transversewall members and said opposing major vide a fluid channelcross-sectional dimension which entransverse faces of each of said lossyattenuator elements.

compasses at least a major portion of the major end faces of said lossyattenuator elements, the common Walls References cued between said fluidcoolant flow channel and said lossy 5 UNITED STATES PATENTS attenuatorelements having thickness dimensions such 2,939,993 6/1960 Zublin et al.31535 that said wall portions are deformable by fluid pressure 3,335,3148/1967 Espinosa et al. 31536 in a manner such as to subject each of saidlossy attenuator elements to oppositely directed compressive forcesHERMAN KARL SAALBACH Primary Exammer' so as to provide a rigid jointbetween each pair of axially 10 S. CHATMON, JR., Assistant Examiner.

